Ethanol: Is it suitable for motorcycles?

American fuel pump ethanol

Americans are crazy about ethanol. Most of their fuel seems to have at least 10% ethanol and the Renewable Fuels Association will have a huge presence at next weekend’s Sturgis Motorcycle Rally, the largest in the world.
They will be providing free ethanol giveaways and free T-shirts at the 2014 Sturgis Buffalo Chip bar at the rally in an effort to convert riders to the natural juice. But is ethanol really any good for your bike?
While the odd dose of ethanol is ok for most bikes and certainly fine for American bikes on a more regular basis, it may cause long-term damage to most others.
Ethanol is a type of alcohol produced by fermentation of crops such as sugarcane or grain. In Australia, ethanol content in unleaded fuel is limited to 10% (E10) but some countries use 85% or even higher in South America.
E10 is becoming more prevalent throughout Australian service stations and NSW service stations even have to stock a minimum requirement of the fuel.
According to the Federal Chamber of Automotive Industries, only post-1986 bikes and ATVs made by BMW, Harley, Polaris and Victory can safely use E10. No Japanese bikes and no Piaggio products can use it. The FCAI doesn’t mention other brands, but it can be assumed ethanol blends are not suitable.
Ethanol doesn’t work with carburettors or mechanical fuel injection. It is also a solvent which attacks metallic and rubber-based fuel lines, and has an affinity to water that can cause steel fuel tanks to rust.
But one of the confusing things for riders is the octane rating. (Octane is a measure of a fuel’s ability to resist engine knocking or pinging which is an uncontrolled burn in the engine that can cause damage. Higher octane fuels resist knocking.)
Most E10 in Australia is rated at 95 RON which seems like it could be suitable for bikes that require that higher octane rating. (In America it has a lot lower RON ratings as their highest RON fuel is only 91.)
But RACQ executive manager technical and safety policy, Steve Spalding, warns that ethanol-blended, higher-octane fuels may not necessarily meet the correct fuel requirements for a vehicle designated to run on PULP.
While the RON may be high enough, there is another property in fuel, called Motor Octane Number (MON), which is rarely specified on the bowser.
MON is usually about 10 numbers lower than RON, so a MON of 85 would be ok for a bike rated at 95 RON.
However, ethanol fuels have much lower MON numbers than their RON which could be too low for your bike.
Either ask the service/gas station for the MON rating or fill up non-ethanol premium unleaded fuel of 95 RON or higher.
It is always best to have a higher octane rating than a lower one even though modern engine management systems have knock sensors that can handle lower octane.
If there is no choice but to fill up with ethanol fuel, make sure your next fill is with a high-octane fuel.
The RFA will be telling riders that ethanol lowers gas/fuel prices, furthers America’s energy security, and revitalises rural America. However, even those debates are far from definitive.
We won’t begin to tackle the environmental concerns which are not proven anyway, but we do believe it is not doing your hip pocket any favours, even though E10 is usually a few cents cheaper.
There is about 3% less energy content in a litre of E10 compared with unleaded fuel which means your engine performance and fuel economy will be 3% worse, or to put it another way, your range will be limited by 3%.
The price of E10 would need to be at least 3% less than ULP for riders to even break even on the fill.


  1. I have been running it in every bike and car I own for 5+ years 95 harley, Dr200 suzuki,89 Enfield, 2 commodores ,68 Impala, lawn mower the lot no bad things happened yet, they even say not to run in Amal carbs but the floats in them are made to handle alcohol fuels and thats what Ethanol is .

  2. It’s not just steel bike tanks that don’t like the stuff – a spate of swelling plastic tanks (Ducati, Aprilia) was attributed to the use of ethanol -content fuels. Some tanks swelled so badly they couldn’t be removed – and if they were, they couldn’t be refitted.
    Ethanol can also rot the in-tank hosing used on submersible pumps and filters, and dissolve the sealant used to conduct wiring into the tank.
    Then there’s the social debate about whether farmers should be growing food, or fuel…

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